1. Field of Invention
This invention relates to sports equipment, specifically to a portable swing analyzer for golf, tennis, baseball, hockey, etc.
2. Prior Art
Golf, baseball, tennis, and hockey are popular sports, which require subtle control over the three-dimension motion of the club, bat, racket, or stick as it contacts the ball or puck. Improvements in performance in these sports require subtle improvement in technique while increasing the force at which the club, bat, racket, or stick contacts the ball or puck. These improvements are typically made in a haphazard, often frustrating, trial and error process because of the lack of qualitative feedback that tells the athlete what he or she is not doing correctly. Real-time quantitative feedback that aids the athlete pinpoint technique weaknesses is very difficult or impossible to obtain.
Good golfers have learned to control the angle of the clubface, the speed of the club head, and the location on the clubface where it contacts the golf ball to attain the results they are looking for. This effect could be a straight shot, a fade or a draw. For a less experienced golfer, this could also include a hook or slice which may send the ball in an unpredictable direction. The same basic principles of three-dimensional control are true for batters, tennis players, and hockey players.
Because of the difficulties that many golfers have in developing a correct swing, several devices that analyze the golf swing have been devised. These devices fall into two broad categories: devices external to the club and devices mounted on or in the club.
The first category of devices analyzes golf swings through the use of specially designed motion sensing apparatuses external to the club. External devices are limited to certain types of practice as it is not possible to carry the device onto a golf course while playing a round. Many also have other limitations related to processing speed, video frame rates, or limited to certain dimensions in order to avoid interfering with the movement of the club. Some of these devices cannot be used with a real golf ball.
The second category, devices attached to the club, can be further divided into visual aids and sensor based measurement systems.
Visual aids are described in a number of patents, such as U.S. Pat. No. 6,139,442 to Wilson, U.S. Pat. No. 3,191,939 to Hooper, and U.S. Pat. No. 2,787,470 to Barrus et al. These visual aids help the golfer “see” the club head movement. This type of analyzer provides a qualitative instantaneous image that can distract the golfer and gives no concrete data as to what is happening to the club head at the moment it contacts the ball.
Other types of visual aids are described in U.S. Pat. No. 3,070,373 to Mathews et al., U.S. Pat. No. 3,820,795 to Taylor and U.S. Pat. No. 3,863,933 to Tredway disclose devices that are attached to the shaft or hosel of a golf club. These devices indicate the path of the swing, not the angle of the clubface.
Sensor based systems that use accelerometers, gyroscopes, angular rate sensors or a combination of the three are described in numerous patent applications including U.S. Pat. Application No. 20020123386 to Shearer et al. and U.S. Pat. Application No. 20030207718 to Perlmutter. While these devices can provide a quantitative measure of performance, systems based on accelerometers, gyroscopes, and/or angular rate sensors, have two serious defects. First, they require exact angular alignment between the sensors and the face of the club and exact positional alignment of the sensors relative to the contact point with the ball. For example, to be able to measure the angle of the clubface relative to the arc of the swing, the sensors need to be aligned precisely with the clubface. This works if the sensors are built into the club head during the manufacturing process, but becomes extremely problematic if the golfer is expected to do the alignment him or herself. In all cases, it is unrealistic to expect a device that requires this type of alignment to be transportable between clubs during a round of golf making it prohibitively expensive to outfit a set of clubs.
Second, accelerometers, gyroscopes, and/or angular rate sensors are all analogue devices. In order to analyze and process the data, the analogue information (usually a voltage or resistance) needs to be latched and then converted to a digital level that can be analyzed by a microprocessor. This latching and conversion process is slow. In golf, with club head speeds as high as 250 km/hr, the contact time between the club head and the ball can be as short as 100 uS. The high-speed accelerometers of today are capable of 800 Hz sample rates, 1,250 uS between samples, for three axis units and cost many hundreds of dollars each. This speed can be increased to 2 KHz by using three independent accelerometers, but this triples the already prohibitive price.
All of the existing portable swing analyzers suffer from one or more of the following disadvantages:                Visual aid swing analyzers do not provide quantitative data, they do not record any characteristics of the swing and thus provide no way of comparing one swing to another to identify what is right or wrong, what can be improved, or if improvement is actually occurring. In addition, visual aid swing analyzers can distract the golfer and require reasonably accurate alignment in order to be effective.        Devices based on the collection of analogue data (accelerometers, gyroscopes, or angular motion sensors), are too slow to detect what happens in 100 uS or so that the club head is in contact with the ball and are prohibitively expensive.        A device based on accelerometers, gyroscopes, or angular motion sensors, requires precision alignment with clubface or in the case of a baseball bat, with the batters hands. This precision alignment requires a high level of skill and special tools and takes a non-trivial amount of time. Keeping the device aligned can be a challenge because most sporting equipment is subject to a certain amount of abuse. This alignment issue makes it unrealistic to move devices based on accelerometers, gyroscopes or angular motion sensors from one club to another during a match.        To avoid the alignment issue, sensors can be built into the piece of sporting equipment. This substantially increases costs, particularly in golf, where it is not uncommon to have 10 or more clubs. In addition, sensors built into the sporting equipment can be a detriment to the correct feeling of the piece of equipment. Lastly, monitoring the batteries in 10 or more golf clubs is a significant burden for the golfer.        External swing analyzers are large and not portable enough to be used while playing a match. In addition, they tend to be very expensive or suffer from issues with processing speed, video frame rate, or lack of analysis related to motion in certain dimensions.        While external swing analyzers and visual aids are both capable of providing real-time technique improving feedback, no portable sensor based swing analyzers are known of today that provide real-time technique improving feedback.        
3. Objects and Advantages
Accordingly, several objects and advantages of the present invention are:                to provide a swing analyzer for golf, tennis, baseball, hockey or similar sport that measures and records all quantitative data important to the athlete relative to the movement of the club, racket, bat, hockey stick or other similar piece of swinging sporting equipment.        to provide a swing analyzer that transfers all recorded data to a computer for in-depth analysis and visualization.        to provide a swing analyzer that is sufficiently fast to capture the contact between the club and the ball while maintaining a low price point.        to provide a swing analyzer which is self aligning.        to provide a swing analyzer which can be transported from one piece of sporting equipment to another and realign itself automatically.        to provide a swing analyzer, which has all the functionality of external swing analyzers, but in a lightweight, portable and low cost package.        to provide a portable device which provides quantitative real-time performance enhancing feedback audibly and/or visually during and immediately after the stroke.        
Further objects and advantages will become apparent from a consideration of the drawings and ensuing description.